Method of multi-radio interworking in heterogeneous wireless communication networks

ABSTRACT

A method of multi-radio interworking to provide integrated cellular and WLAN access for a multi-radio device is provided. A serving base station in a cellular network first obtains wireless local area network (WLAN) information and then forward the WLAN information to a serving device such that the serving device is capable to connect with both the cellular network and a WLAN. The WLAN information may comprise scanning information, WLAN QoS information, WLAN layer-3 information, or additional WLAN access point information. The WLAN information is forwarded based on triggering events associated with the serving base station information, WLAN coverage information, or the serving device information. Based on the received WLAN information, when entering WLAN coverage, the serving device activates its WLAN access to forward traffic from the cellular access network to the WLAN access network. When leaving WLAN coverage, the serving device deactivates its WLAN access to save power consumption.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation, and claims priority under 35 U.S.C.§ 120 from nonprovisional U.S. patent application Ser. No. 15/082,144,entitled “METHOD OF MULTI-RADIO INTERWORKING IN HETEROGENEOUS WIRELESSCOMMUNICATION NETWORKS,” filed on Mar. 28, 2016, the subject matter ofwhich is incorporated herein by reference. Application Ser. No.15/082,144, in turn, is a continuation, and claims priority under claimspriority under 35 U.S.C. § 120 from nonprovisional U.S. patentapplication Ser. No. 13/065,038, entitled “METHOD OF MULTI-RADIOINTERWORKING IN HETEROGENEOUS WIRELESS COMMUNICATION NETWORKS,” filed onMar. 11, 2011, the subject matter of which is incorporated herein byreference. Application Ser. No. 13/065,038, in turn claims priorityunder 35 U.S.C. § 119 from U.S. Provisional Application No. 61/313,182,entitled “Method of Smart Interworking to Support Integrated Multi-RadioWireless Communication Terminals in Heterogeneous Wireless CommunicationNetworks,” filed on Mar. 12, 2010; U.S. Provisional Application No.61/423,160, entitled “Method of Smart Interworking to Offload Trafficfrom Cellular Network to WiFi Network,” filed on Dec. 15, 2010; thesubject matter of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless networkcommunication, and, more particularly, to multi-radio interworking inheterogeneous wireless communication networks.

BACKGROUND

Demand on mobile data service continues to grow dramatically in therecent years. The growth in demand is driven by modern portable handhelddevices, such as smart phone, tablet PC, portable router etc. The growthin demand is also driven by new applications, such as streaming video,e-book, online gaming etc. Studies have shown that the demand for mobiledata service is expected to grow more than fifty times from year 2008 to2013.

To meet this fast growing demand in mobile data service, various networkoperators are developing new technologies and defining new standards forthe next generation wireless networks to achieve much higher peaktransmission rate. For example, 1 Gbps peak transmission rate isrequired by ITU-R for IMT-Advanced systems in the 4th generation (“4G”)mobile communications systems. 1 Gbps peak transmission rate in wirelessnetworks can provide users similar experience as in wireline networks,and it is sufficient to satisfy most applications on the Internet todayand in the near future.

While peak transmission rate is no longer a critical problem after 4Gera, network capacity is likely to be exhausted very soon in the nextfew years. Not only traffic demand is growing dramatically (i.e., >50×in 5 years), but also the improvement on average cell spectralefficiency is very limited from 3G to 4G era (i.e., <10×). In addition,the available spectrum resource is also limited. Network capacity willstill be exhausted very soon even all the networks are upgraded with 4Gair interface. This problem in fact already happens in some areas.Therefore, capacity exhaustion is anticipated to be the most criticalproblem during 4G and beyond 4G (B4G) era.

While the demand on wireless communication service continues toincrease, the demand on broadband access may not always require mobilitysupport. In fact, studies have shown that only a small fraction of usersdemand on simultaneous mobile and broadband access. Therefore, inaddition to cellular networks, there are other networks able to deliverinformation to mobile users, with or without mobility support. In mostgeographic areas, multiple radio access networks (RANs) such as E-UTRANand WLAN are usually available. Furthermore, wireless communicationdevices are increasingly being equipped with multiple radio transceiversfor accessing different radio access networks. For example, a multipleradio terminal (MRT) may simultaneously include Bluetooth, WiMAX, andWiFi radio transceivers. Thus, multi-radio integration becomes morefeasible today and is the key to help user terminals to explore morebandwidth available from different radio access technologies and achievebetter utilization of scarce radio spectrum resources.

Multi-radio integration needs to be achieved from two perspectives. Fromthe network perspective, much research has already been done since 3Gera on inter-networking for traffic routing and offloading in thebackhaul (i.e., wireline) network. On the other hand, from the deviceperspective, certain research has just been initiated to investigate howdifferent radio access networks can interwork with each other to preventmutual interference. However, it has not been well studied on howdifferent radio interfaces of the same device can interwork to improvetransmission efficiency, and how radio access networks can help thedevice with shared components for different radio interfaces to workwell together.

SUMMARY

A method of multi-radio interworking to provide integrated cellular andWLAN access for a multi-radio device in a wireless communication networkis provided. A serving base station in a cellular network first obtainswireless local area network (WLAN) information of a WLAN and thenforward the WLAN information to a serving device such that the servingdevice is capable to connect to both the cellular network and the WLAN.The WLAN information may comprise scanning information, WLAN QoSinformation, WLAN layer-3 information, or additional WLAN access point(AP) information.

The WLAN information is forwarded by the serving base station to theserving device based on certain triggering events associated with theserving base station information, WLAN coverage information, or theserving device information. For example, the triggering events may beassociated with the serving base station cell coverage, WLAN coverageinformation including a WLAN AP location and the WLAN service coverage,and the serving device information including device location, devicefootprint, device measurement result over the serving base station, ordevice WLAN capability.

Based on the received WLAN information, when entering WLAN coverage, theserving device activates access to the WLAN via its WLAN transceiver tooffload traffic from the cellular access network to the WLAN accessnetwork. When leaving WLAN coverage, the serving device timelydeactivates access to the WLAN via its WLAN transceiver to save powerconsumption. Therefore, by obtaining and forwarding the WLANinformation, the serving base station in a cellular network is able toassist its serving device to offload traffic to a WLAN network toimprove efficiency and utilization.

Other embodiments and advantages are described in the detaileddescription below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 illustrates multiple radio access networks for a user terminal toaccess information source in accordance with one novel aspect.

FIG. 2 illustrates an example of multi-radio integration with integratedcellular plus WLAN access.

FIG. 3 illustrates multi-radio coexistence as the first stage intechnology migration roadmap.

FIG. 4 illustrates multi-radio cooperation as the second stage intechnology migration roadmap.

FIG. 5 illustrates multi-radio cognition as the third stage intechnology migration roadmap.

FIG. 6 illustrates an example of multi-radio interworking of a userterminal in a cellular network having WLAN coverage.

FIG. 7 illustrates a first step in WLAN offload operational procedure.

FIG. 8 illustrates a second step in WLAN offload operational procedure.

FIG. 9 illustrates one embodiment of a complete WLAN offload procedurein accordance with one novel aspect.

FIG. 10 illustrates an overview of network architecture for WLANoffload.

FIG. 11 illustrates one embodiment of using paging procedure to initiatea WLAN offload procedure.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 illustrates multiple radio access networks for a user terminal 11to access information source 10 in accordance with one novel aspect. Aradio access network (RAN) is part of a mobile telecommunication systemimplementing a radio access technology. In most geographic areas,multiple radio access networks are usually available for user terminal11 to access information source 10 (e.g., the Internet) and obtainmobile data service. Examples of different radio access network typesare GSM radio access network, UTRA or E-UTRA cellular access network,WiMAX system, and Wireless Local Area Network (WLAN). If the multipleRANs support the same air interface, then the entire access network is ahomogeneous network. On the other hand, if the multiple RANs supportdifferent air interfaces (e.g. cellular and WiFi), then the entireaccess network is a heterogeneous network. From a user terminal point ofview, it does not matter which access network the desired information isdelivered through, as long as data service is maintained with fast speedand high quality. In accordance with one novel aspect, with multi-radiointegration, user terminal 11 is a multi-radio terminal (MRT) and isable to explore more bandwidth available from different radio accessnetworks, both homogeneous and heterogeneous, for improved per terminalperformance and/or optimized radio resource utilization.

Depending on the standard, a user terminal or mobile phone is varyinglyknown as user equipment (UE), terminal equipment, and mobile station(MS) etc. In the example of FIG. 1, user terminal 11 is referred to asUE11, and is equipped with both a cellular radio module and a WiFi radiomodule. UE11 may access the Internet via an E-UTRAN path (denoted by adashed line with single dot) using its cellular module. Alternatively,UE11 may access the Internet via a WLAN path (denoted by a dashed linewith double dots) using its WiFi module. In one advantageous embodiment,the cellular radio module and the WiFi radio module of UE11 cooperateswith each other to provide integrated cellular and WiFi access over bothE-UTRAN 12 and WLAN 13 to improve transmission efficiency and bandwidthutilization.

FIG. 2 illustrates an example of multi-radio integration with integratedcellular (e.g., E-UTRAN) and WiFi (e.g., WLAN) access. E-UTRAN is thecellular air interface of 3GPP Long Term Evolution (LTE) upgrade pathfor mobile networks. It is the abbreviation for Evolved UMTS TerrestrialRadio Access Network, also known as the Evolved Universal TerrestrialRadio Access (E-UTRA) in early drafts of the 3GPP LTE specification. Onthe other hand, WiFi is a term that describes a range of connectivitytechnologies including Wireless Local Area Network (WLAN) based on theIEEE 802.11 standards, device-to-device connectivity, and a range oftechnologies that support PAN, LAN, and even WAN connectivity. In theexample of FIG. 2, user equipments UE21, UE22, and UE23 are locatedwithin the cell coverage of a base station eNB24 in a cellular E-UTRANradio access network. In addition, UE22, and UE23 are also locatedwithin the coverage of a WiFi access point WiFi AP25 in a WLAN accessnetwork.

As illustrated in the top half of FIG. 2, user equipments UE21-23 areserved by serving base station eNB24 via an established LTE channel fordata communication (denoted by slashed shade). User equipments UE21-23,however, do not establish any WLAN channel with WiFi AP25 for datacommunication (denoted by white shade). For example, without multi-radiointegration technology, user equipments UE21-23 are not even aware ofthe existence of WiFi AP25 and the availability of any WLAN access. Itcan be seen that, without multi-radio interworking, network bandwidth ofthe WLAN access network is not utilized by the user equipments UE21-23at all.

On the other hand, as illustrated in the bottom half of FIG. 2, userequipments UE21-23 are served by serving base station eNB24 via anestablished LTE channel for data communication (denoted by slashedshade). In addition, user equipments UE22-23 also establish a WLANchannel with WiFi AP25 to offload data traffic from the LTE channel tothe WiFi channel (denoted by slashed shade). For example, the servingbase station eNB24 in the cellular network may inform UE22-23 theavailability of WLAN access through WiFi AP25 using multi-radiointegration technology. It can be seen that, with multi-radiointerworking, network bandwidth of both the E-UTRAN and the WLAN accessnetwork are efficiently utilized by the user equipments UE21-23 toimprove transmission efficiency.

In one advantageous aspect, the network operator of the cellular networkmay have established certain business service agreement with the networkoperator of the WLAN network to facilitate the above-describedmulti-radio integration and interworking. In one example, the networkoperator of the cellular network may be the same entity as the networkoperator of the WLAN network. In a first scenario, the network operatorcharges a flat fee on its users for aggregated mobile data service. In asecond scenario, the network operator charges its fee based ontransmitted data volume. In both scenarios, via the above-describedmulti-radio interworking, the network operator is able to provide betterservice to the users while charging comparable fees.

Multi-radio integration does not happen overnight. Instead, it requireslong-term planning with a well-defined technology migration roadmap. Ingeneral, the first stage in the technology migration roadmap is definedas multi-radio coexistence stage, during which multiple radio interfacesco-exist in the same terminal and are able to mitigate interference suchthat different radio access networks can work well independently. Thesecond stage in the technology migration roadmap is defined asmulti-radio cooperation stage, during which multiple radio interfacesare able to interwork with each other in the same terminal such thatradio resources over different networks are leveraged for better perterminal performance. The third and final stage in the technologymigration roadmap is defined as multi-radio cognition stage, duringwhich multiple radio interfaces are able to interwork with each otherfor resource optimization such that the same radio resource can beflexibly shared by different radio interfaces. The three differentstages are now described below with accompanying drawings.

FIG. 3 illustrates multi-radio coexistence as the first stage inmulti-radio integration technology migration roadmap. During the stageof multi-radio coexistence, multiple radio modules co-exist in amulti-radio terminal (MRT) for simultaneous and independent datacommunication over different systems (e.g., system #1 over RF carrier #1and system #2 over RF carrier #2 as illustrated in FIG. 3). Theobjective of this stage is to mitigate the coexistence interference fromthe radio modules co-located on the same device platform. In the exampleof FIG. 3, MRT 31 comprises a first radio transceiver including a firstRF module (RF#1), a first baseband module (BB#1), and a first antenna(ANT#1), and a second radio transceiver including a second RF module(RF#2), a second baseband module (BB#2), and a second antenna (ANT#2).For example, RF#1 is a Bluetooth (BT) module and RF#2 is a cellularmodule. Simultaneous operation of the multiple radio transceiversco-located on the same physical device, however, can suffer significantdegradation including significant interference between them because ofthe overlapping or adjacent radio spectrums. Due to physical proximityand radio power leakage, when the transmission of data for RF#1 overlapswith the reception of data for RF#2 in time domain, the reception ofRF#2 may seriously suffer due to interference from the transmission ofRF#1. Likewise, data transmission of RF#2 may also interfere with datareception of RF#1.

Research has already been initiated to investigate how different radioaccess networks could interwork with each other to prevent mutualinterference. Various methods of scheduling transmitting and receivingtime slots for co-located radio transceivers have been proposed. Forexample, a BT device (e.g., RF#1) first synchronizes its communicationtime slots with a co-located cellular radio module (e.g., RF#2), andthen obtains the traffic pattern of the co-located cellular radiomodule. Based on the traffic pattern, the BT device selectively skipsone or more TX or RX time slots to avoid data transmission or receptionin certain time slots and thereby reducing interference with theco-located cellular radio module. The skipped time slots are disabledfor TX or RX operation to prevent interference and to achieve moreenergy saving. For additional details on multi-radio coexistence, see:U.S. patent application Ser. No. 12/925,475, entitled “System andMethods for Enhancing Coexistence efficiency for multi-radio terminals,”filed on Oct. 22, 2010, by Ko et al. (the subject matter of which isincorporated herein by reference).

FIG. 4 illustrates multi-radio cooperation as the second stage inmulti-radio integration technology migration roadmap. During the stageof multi-radio cooperation, multiple radio modules interwork with eachother in a multi-radio terminal (MRT) for efficient data communicationover different systems (e.g., system #1 over RF carrier #1 and system #2over RF carrier #2 as illustrated in FIG. 4). The objective of thisstage is efficient inter-networking to help the MRT to maintainconnections in multiple systems with reduced hardware complexity. Fromsystem operation point of view, MRT41 maintains logical connection withsystem #1 (denoted by dashed shade) while being able to offload datatraffic to system #2 (denoted by dotted shade). New protocols may berequired in this cooperation stage to help MRT41 to switch between twosystems without losing control signals and connectivity. From devicestructural point of view, MRT 41 may comprise a common radio frequencymodule (COMMON RF), two independent baseband modules (BB #1 and BB #2),and two separate antennas (ANT#1 and ANT#2).

FIG. 5 illustrates multi-radio cognition as the third stage inmulti-radio integration technology migration roadmap. During the finalstage of multi-radio cognition, multiple radio modules interwork witheach other in a multi-radio terminal (MRT) for optimized datacommunication over different radio access networks in the same system.The objective of this stage is to optimize radio (spectrum) resourceutilization while minimizing hardware complexity. Ideally, unnecessarywaste on radio resource over all considered spectrum portions isprevented. From system operation point of view, MRT51 is connected tosystem #1 and receives control signal in system #1 over carrier #1(denoted by slashed shade). In addition, MRT51 also receives data signalin system #1 over carrier #2 (denoted by dotted shade). This is becauseMRT51 is able to switch between different RF carriers together with itsserving base station or WiFi access point in the same system. Moreover,a different user may simultaneously obtain data service over carrier #1in system #1 (denoted by grey-fill shade). From device structural pointof view, MRT 51 may comprise a common radio frequency module (COMMONRF), a common baseband module (COMMON BB), and two separate antennas(ANT#1 and ANT#2). By achieving radio resource sharing with minimizedhardware complexity, multi-radio cognition is the final stage to bereached in the near future for multi-radio interworking.

While research has been initiated to investigate how different radioaccess networks could interwork with each other to prevent mutualinterference during the multi-radio coexistence stage, it has not beenwell studied on how different radio interfaces of the same device caninterwork to improve transmission efficiency. Especially, it has notbeen well studied on how radio access networks can help the device withshared components for different radio modules and transceivers to workwell together. It has been realized, however, multi-radio integration isdifficult to achieve without network and system support. This problembecomes more serious when considering multi-radio cooperation andcognition. For example, user terminal does not know the time instance itcan switch to different carriers in FIGS. 4 and 5. Without properassistance, user terminal needs to be designed in response to the worstscenario, e.g., simultaneous transmit and receive by different radiotransceivers.

FIG. 6 illustrates an example of multi-radio interworking of a userterminal in a cellular network having WLAN coverage in accordance withone novel aspect. The example of FIG. 6 takes cellular network (e.g.,LTE) as system #1 and WiFi (e.g., WLAN) as system #2 with respect toFIGS. 4 and 5. The example of FIG. 6 also takes traffic offloading(e.g., forwarding) as one main embodiment of multi-radio interworking.More specifically, data traffic of the user terminal can be offloadedfrom a cellular access network to a WLAN access network to improvetransmission efficiency. It should be noted, however, that the problemis generic and the solution is applicable to many other systemcombinations.

In the example of FIG. 6, cellular radio access network E-UTRAN 61comprises a serving base station eNB62, and WLAN 63 comprises a WiFiaccess point AP64. User equipment UE65 and AP64 are both located withinthe cell coverage provided by eNB62. UE65 is initially served by itsserving base station eNB62 via LTE cellular air interface at a firstlocation A. When UE65 moves to a second location B later, it is thenlocated inside the coverage provided by WiFi AP64 for WLAN access.Subsequently, UE65 moves to a third location C, where WLAN access is nolonger available.

Without multi-radio integration, UE65 served by eNB62 cannot connect ordisconnect to WiFi AP64 efficiently. Because of the limited WLANcoverage, UE65 has no idea when to scan WiFi AP64. The current method isthat WiFi service provider may advertise its WiFi availability in somespecific areas such as McDonald, café, restaurant, etc. The user of UE65then manually activates the WLAN module to scan and access the WLANnetwork. The user, however, may not notice the WiFi advertisement andthus may not activate the WLAN module immediately after moving inside ofthe WLAN coverage. In addition, the user may forget to deactivate theWLAN module when moving outside of the WLAN coverage.

As illustrated by timeline 66 in FIG. 6, the user of UE65 moves tolocation B at time T0. The user manually activates the WLAN module ofUE65 to scan WiFi AP64 and access WLAN 63 at time T1. UE65 is connectedto WLAN 63 at time T2 after WLAN connection setup. Effective WLANtraffic offload then occurs from time T2 to time T3. At time T3, theuser moves outside of the WLAN coverage. Finally, the user remembers todeactivate the WLAN module of UE65 at time T4. As a result, the cellularnetwork E-UTRAN 61 is not able to offload traffic to WLAN 63 for UE65when the user forgets to turn on the WLAN module of UE65 from time T0 toT1. In addition, UE65 wastes power consumption when the user forgets toturn off the WLAN module of UE65 from time T3 to T4. From timeline 66,it can be seen that although UE65 is located within WLAN coverage fromtime T0 to T3, the actual WLAN traffic offload time period (from time T2to T3) is very short, at the cost of activating the WLAN module for arelative long time period (from time T1 to T4).

On the other hand, with multi-radio integration, UE65 has certaininformation on WLAN 63 including the WLAN access and coverageinformation and thus can connect or disconnect to WiFi AP64 efficiently.In general, when a UE served by a serving base station in a cellularnetwork enters a location with WLAN access, WLAN access will beactivated via its WLAN module and WLAN connection setup will be startedautomatically after entering the WLAN coverage area. As a result, the UEwill have established connection to both the cellular network and theWLAN. Furthermore, the serving base station in the cellular network mayassist the UE during connection setup to reduce the setup time. When theUE leaves the WLAN coverage area, WLAN access will be timely deactivatedvia its WLAN module to save power consumption.

As illustrated by timeline 67 in FIG. 6, the user moves to location B attime T0. At the same time T1=T0, the WLAN module of UE65 is activated toscan WiFi AP64 and access WLAN 63. At time T2, UE65 is connected to WLAN63 and data traffic of UE65 is offloaded from E-UTRAN 61 to WLAN 63. Attime T3, the user moves outside of the WLAN coverage area. Finally, atthe same time T4=T3, the WLAN module of UE65 is deactivated to savepower consumption. From timeline 67, it can be seen that when UE65 islocated within WLAN coverage from time T0 to T3, data traffic of UE65 isoffloaded from E-UTRAN 61 to WLAN 63 to improve transmission efficiencyduring a majority of time period (from time T2 to T3). Furthermore, theconnection setup time (from time T1 to T2) is shorter as compared totimeline 66, and the WLAN activation time (from T1 to T4) is shorter ascompared to timeline 66 without multi-radio interworking.

To facilitate the above-described traffic offloading from a cellularaccess network to a WLAN, it is necessary for a UE to obtain certainWLAN information. For example, it is desirable for the UE to know whenit should activate the WLAN module, where to scan WiFi AP over whichWiFi channel, which WiFi AP it can or prefer to access, how to completethe WLAN setup with reduced time, and when to deactivate the WLANmodule. In accordance with one novel aspect, the serving eNB of the UEwill first obtain the WLAN information (e.g., a first step illustratedbelow in FIG. 7), and then forward the WLAN information to the UE undersome triggering events to facilitate the WLAN offload operationalprocedure (e.g., a second step illustrated below in FIG. 8).

FIG. 7 illustrates a first step in WLAN offload operational procedure ina cellular network 70. Cellular network 70 comprises a plurality of basestations (eNBs) including eNB71, eNB72, and eNB73, and a plurality ofserving devices (UEs) including UE74, UE75, and UE76. The cell coverageof some of the eNBs overlaps with the coverage of a plurality of WLANs,and each WLAN comprises a WiFi access point (AP) including AP77, AP78,and AP79 to provide WLAN access. In the example of FIG. 7, serving basestation eNB71 serves serving device UE74, which is located inside theWLAN coverage provided by WiFi AP77. Similarly, serving base stationseNB72-eNB73 serve serving devices UE75-UE76, which are located insidethe coverage provided by WiFi AP78-AP79, respectively.

For UEs that have established connection with a corresponding WiFi AP,or for UEs that have performed scanning over a corresponding WiFi AP(e.g., as denoted by dashed arrows in FIG. 7), they have obtainedcertain WLAN information based on the UE scanning result. In accordancewith one novel aspect, these UEs can transmit the WLAN information toits serving eNB (e.g., as denoted by solid arrows in FIG. 7). Forexample, UE74 obtains WiFi AP77 information via scanning and thentransmits the information to eNB71. Similarly, UE75-UE76 obtains WiFiAP78-AP79 information via scanning and then transmits the information toeNB72-eNB73. The serving base stations then understand which WiFi AP hascoverage overlapped with which cell coverage in the cellular network.

FIG. 8 illustrates a second step in WLAN offload operational procedurein cellular network 70. In the second step of WLAN offload operationalprocedure, the serving base stations in the cellular network forward theobtained WLAN information to their serving devices based on certaintriggering events. In the example of FIG. 8, UE81 moves toward eEB71 andhandovers from eNB84 to eNB71. When UE81 handovers to eNB71 (e.g., oneof the triggering events), eNB71 forwards the obtained WLAN information(e.g., WiFi AP77 information) to UE81. As a result, when UE81 movestoward a location with WLAN coverage, UE81 automatically activates WLANaccess via its WLAN module to search and connect with WiFi AP77 based onthe WLAN information offered by eNB71. Similarly, when UE81 moves awayfrom the location with WLAN coverage, UE81 automatically deactivatesWLAN access via its WLAN module to save power.

Handover is only one of the triggering events for a serving base stationto forward WLAN information to its serving device. The triggering eventsmay be associated with the serving base station information such as theserving eNB location and coverage information (e.g., when a UE handoversto the serving eNB), WLAN coverage information such as its WiFi APlocation (e.g., identified by GNSS or network positioning) and coverage(e.g., identified WiFi AP within eNB cell coverage), and the servingdevice information such as device location (e.g., identified by GNSS ornetwork positioning), device footprint (e.g., a list of cell IDidentified by the serving UE connected with that WiFi AP with or withoutthe associated measurement results), device measurement results (e.g.,by RSRP, RSRQ, or CQI of the serving or neighboring eNB), and deviceWiFi capability previously reported to the serving eNB.

FIG. 9 illustrates one embodiment of a complete WLAN offload procedurein a cellular network in accordance with one novel aspect. The cellularnetwork comprises a serving base station eNB91, user equipments UE92 andUE93, and a WiFi access point AP94 that provides overlapping WLANcoverage with the cell coverage of eNB91. Both UE92 and UE93 areequipped with a WLAN module and a cellular module. Alternatively, UE92and UE93 may be equipped with a common RF module that can be shared forWLAN and LTE access. In the example of FIG. 9, UE93 is located withinWLAN coverage provided by WiFi AP94. UE93 performs scanning and therebyobtains scanning result over the WLAN frequency channels used by WiFiAP94 (step 101). The scanning result may comprise the service setidentifier (SSID) of WiFi AP94, the frequency channel used by WiFi AP94,the received signal strength, the WLAN signal and/or protocol version(e.g., IEEE 802.11a/b/g/n), the WLAN mode (e.g., infrastructure mode,ad-hoc mode, or portable router), and the IP address of WiFi AP94. Thescanning result may further comprise WLAN connection quality (QoS)information such as the service latency and the achievable throughput ofWiFi AP94, the location when WiFi AP94 was scanned or connected by UE93,the footprint when WiFi AP94 was scanned or connected by UE93, and themeasurement results by UE93 over the cellular network when UE93 scannedor is connected to WiFi AP94.

Next, UE93 transmits the scanning result to its serving eNB91 (step102). As a result, eNB91 obtains WLAN information based on the scanningresult. The obtained WLAN information generally is very helpful forother UEs (e.g., UE92) to determine whether it should activate its WLANmodule and where to scan for WiFi APs. In addition to obtaining the WLANinformation based on the scanning result described above, eNB91 mayobtain the WLAN information or additional WLAN information through othermechanism, such as from the server in backhaul network or from the WiFiAP itself. For example, the WLAN information may further comprise WLANlayer-3 information (e.g., WLAN gateway IP address, DNS IP address, DHCPserver IP address), device IP address to be used in WLAN, and I-WLANinformation (e.g., wireless access gateway (WAG) address, availablepublic land mobile network (PLMN) attached to this WLAN). In anotherembodiment, the WLAN information may comprise additional information tohelp the device to determine which WiFi AP it can access, prefers toaccess, or is disallowed to access. Furthermore, the WLAN informationmay comprise authentication information and requirement by the WiFi AP,the charging policy of the WiFi AP, the access priority of the WiFi AP(e.g., high priority to cellular operator's own WiFi AP), the requiredregistration information by the WiFi AP, the loading of the WiFi AP, theremaining capacity of the WiFi AP, the achievable throughput of the WiFiAP, and the service latency of the WiFi AP.

In one embodiment, eNB91 may indicate to the UE the prioritized WiFi APto be accessed based on the cellular operator's policy. In one example,the WiFi AP deployed by serving operator itself (e.g. CMCC) or the WiFiAP deployed by the other operator who has roaming agreement with theserving operator has higher priority. In another example, the cellularoperator may not want UE to access other public WiFi AP in order tomaximize its revenue from data access if the charging is based ontransmitted data volume. In yet another example, the cellular operatormay want UE to access public WiFi AP as much as possible if the chargingis by flat rate. In another embodiment, different WLAN access policy canbe applied when the WiFi AP is connected with different backhaul (e.g.,wireline broadband backhaul or wireless backhaul). For example, acellular network operator may not want the UEs to use WiFi to connectwith another portable WiFi router because the portable WiFi routerconsumes the same wireless resource from the cellular network and thuscannot efficiently offload any traffic from the cellular network.

After UE92 handovers to serving eNB91 (step 103), the handover eventtriggers eNB91 to forward the obtained WLAN information to UE92 (step104). After receiving the WLAN information, UE92 activates WLAN accessvia its WLAN module when it moves inside WLAN coverage (step 105). Basedon the received WLAN information, UE92 performs scanning over WLANchannels and starts to setup connection with WiFi AP94 (step 106). TheWLAN connection setup may takes a long time because of various securityrelated procedures including authentication and registration. Forexample, some WiFi AP will require authentication process involving userentering ID and password. To help reducing the connection setup time,the serving eNB91 may perform a series of actions includingpre-authentication and pre-registration (step 107). For example, eNB91may help to perform pre-authentication with WiFi AP94 using UE92'sidentify previously registered in the cellular network, to acquire WLANaccess key and pass to UE92 for WiFi AP access, to pre-authenticate orpre-register UE92 to the PLMN attached to the WLAN using UE92's identity(e.g., SIM), to inform PDG to redirect selected UE packet data trafficto the WLAN, and to forward security information for accessing WiFi AP94to UE92. After WLAN connection setup, UE92 is connected to both thecellular network and the WLAN (step 108). Data traffic of UE92 can beforwarded from the cellular network to the WLAN to improve performanceand efficiency.

When UE92 later on leaves outside of WLAN coverage, it deactivates WLANaccess via its WLAN module based on certain triggering conditions (step109). The triggering conditions may be based on a notification from theserving eNB91 about the unavailability of any WiFi AP, the serving cellof UE92, the location of UE92, the footprint of UE92, the threshold ofthe measurement result over the serving eNB91, the threshold of the WLANsignal strength, and the threshold of achievable WLAN throughput. Forexample, UE92 may deactivate its WLAN module when UE92 enters anothercell where UE92 receives no WiFi AP information from the eNB that servesthe cell. UE92 may also deactivate its WLAN module when scanning resultshows that the received signal strength from the WiFi APs indicated bythe serving eNB91 are below certain threshold.

A radio access network (RAN) is only part of a wireless communicationnetwork implementing a radio access technology. FIG. 10 illustrates anoverview of network architecture for WLAN offload in a wirelesscommunication network 110. Wireless communication network 110 comprisesa radio access network RAN 111 and an evolved packet core network 112.RAN 111 comprises an E-UTRAN 113 including a plurality of eNBs and aWLAN 114 including a WiFi AP and a wireless access gateway (WAG) 115,and each RAN provides radio access for user equipment UE121 viadifferent air interfaces. Evolved packet core network 112 comprises amobility management entity (MME) 116, a serving gateway (S-GW) 117, apacket data network gateway (PDN-GW) 118, and an enhanced PDN gateway(ePDN) 119. Evolved packet core network 112 and E-UTRAN 113 together isalso referred to as a public land mobile network (PLMN). From UE121perspective, it is equipped with both a cellular transceiver and a WiFitransceiver, and is able to access application networks or the Internet120 via cellular access (e.g., the E-UTRAN path denoted by dashed linewith single dot) or WLAN access (e.g., the WLAN path denoted by dashedline with double dots).

FIG. 11 illustrates one embodiment of using paging procedure to initiatea WLAN offload procedure in wireless communication network 110. In theexample of FIG. 11, a network server 122 uses paging procedure toinitiate or update the WLAN offload procedure. In step 1, network server122 transmits a service initiation message to PDG 118 for sending apaging message to UE121. The paging message contains information of thetarget WLAN for UE121 to access. In step 2, PDG 118 transmits the pagingmessage to MME 116, which in turn forwards the paging message to UE121via E-UTRAN access network 113. The paging message informs UE121 thatwhenever UE121 wants to establish connection for data service, UE121should establish such connection through WLAN access network 114,instead of through E-UTRAN access network 113. In step 3, UE121 startsWLAN offload setup with WAG 115 and then transmits a paging responsethrough WLAN access network 114 to the network entity that issues thepaging message (e.g., PDG 118). In step 4, after paging response, WLANconnection is established and packet data service flow is establishedthrough WLAN access network 114.

Paging procedure is only one example in initiating the WLAN offloadprocedure. A paging message is one type of radio resource control (RRC)message that is used to transmit and forward WLAN information. Ingeneral, the WLAN information may be carried by various types ofmessages including the RRC message in UTRA or E-UTRA systems, the mediaaccess control (MAC) control element (CE) in UTRA or EUTRA systems, andthe MAC management message in WiMAX systems.

Although the present invention has been described in connection withcertain specific embodiments for instructional purposes, the presentinvention is not limited thereto. Accordingly, various modifications,adaptations, and combinations of various features of the describedembodiments can be practiced without departing from the scope of theinvention as set forth in the claims.

What is claimed is:
 1. A method, comprising: receiving information of awireless local area network (WLAN) by a user equipment (UE) forwardedfrom a serving base station based on triggering events associated withthe serving base station information, WLAN coverage information, or theUE information, wherein the WLAN information is obtained by the servingbase station from a mobile device in a cellular network, and wherein theWLAN information comprises scanning results of the WLAN obtained by themobile device, and wherein the WLAN information is either forwardedusing a paging procedure of a packet core network that the cellularnetwork belongs to, or contained in a downlink radio resource control(RRC) message, or contained in a media access control (MAC) controlelement (CE) of a downlink signal, or contained in a downlink MACmanagement message in the cellular network; establishing a connectionwith the WLAN based on the received WLAN information; and offloadingdata traffic between the serving base station and the UE from thecellular network to the WLAN, wherein the UE connects with both theserving base station and the WLAN such that data traffic is sharedbetween the serving base station and the WLAN.
 2. The method of claim 1,wherein the WLAN information comprises a service set identifier (SSID)of a WLAN access point (AP) or a frequency channel used by the WLAN AP.3. The method of claim 2, wherein the WLAN information comprises theaccess priority or principle associated with the SSID of the WLAN AP. 4.The method of claim 2, wherein the WLAN information comprises thebackhaul type connected by the WLAN AP.
 5. The method of claim 1,wherein the WLAN information comprises received signal strength, WLANsignal/protocol version, and WLAN mode of a WLAN access point (AP). 6.The method of claim 1, wherein the WLAN information comprises layer-3information including at least one of a WLAN AP gateway IP address, aDNS IP address, a DHCP server IP address, a device IP address to be usedin the WLAN, and I-WLAN information.
 7. The method of claim 1, furthercomprising: performing pre-authentication and pre-registration with aWLAN access point (AP) based on the UE identity registered in thecellular network; and receiving a WLAN access key of the WLAN AP by theUE, wherein the WLAN access key is acquired by the serving base station.8. The method of claim 1, further comprising: receiving WLAN accessinformation by the UE for WLAN access, wherein the WLAN accessinformation is acquired by the serving base station.
 9. The method ofclaim 1, wherein the WLAN information comprises information about a WLANaccess point (AP) including at least one of authentication information,charging policy, access priority, registration information, loading,capacity, achievable throughput, and service latency of the WLAN AP. 10.The method of claim 1, wherein the WLAN information is received by theserving base station from a second UE, and wherein the WLAN informationcomprises scanning result obtained by the second UE over WLAN frequencychannels.
 11. The method of claim 1, wherein the triggering event isassociated with the serving base station cell coverage.
 12. The methodof claim 1, wherein the triggering event is associated with WLANcoverage information including a WLAN AP location and the WLAN servicecoverage.
 13. The method of claim 1, wherein the triggering event isassociated with the UE information including device location, devicefootprint, device measurement result over the serving base station, ordevice WLAN capability.
 14. A user equipment (UE), comprising: acellular radio frequency (RF) transceiver that transmits and receives RFsignals in a cellular network; a wireless local area network (WLAN) RFtransceiver that transmits and receives RF signals in a WLAN network; aWLAN information circuit that receives information of the WLAN forwardedfrom a serving base station based on triggering events associated withthe serving base station information, WLAN coverage information, or theUE information, wherein the WLAN information is obtained by the servingbase station from a mobile device in a cellular network, and wherein theWLAN information comprises scanning results of the WLAN obtained by themobile device, and wherein the WLAN information is either forwardedusing a paging procedure of a packet core network that the cellularnetwork belongs to, or contained in a downlink radio resource control(RRC) message, or contained in a media access control (MAC) controlelement (CE) of a downlink signal, or contained in a downlink MACmanagement message in the cellular network; a WLAN connection circuitthat establishes a connection with the WLAN based on the received WLANinformation; and a data traffic circuit that offloads data trafficbetween the serving base station and the UE from the cellular network tothe WLAN, wherein the UE connects with both the serving base station andthe WLAN such that data traffic is shared between the serving basestation and the WLAN.
 15. The UE of claim 14, wherein the WLANinformation comprises a service set identifier (SSID) of a WLAN accesspoint (AP) or a frequency channel used by the WLAN AP.
 16. The UE ofclaim 15, wherein the WLAN information comprises the access priority orprinciple associated with the SSID of the WLAN AP.
 17. The UE of claim15, wherein the WLAN information comprises the backhaul type connectedby the WLAN AP.
 18. The UE of claim 14, wherein the WLAN informationcomprises received signal strength, WLAN signal/protocol version, andWLAN mode of a WLAN access point (AP).
 19. The UE of claim 14, whereinthe WLAN information comprises layer-3 information including at leastone of a WLAN AP gateway IP address, a DNS IP address, a DHCP server IPaddress, a device IP address to be used in the WLAN, and I-WLANinformation.
 20. The UE of claim 14, wherein the WLAN informationcomprises information about a WLAN access point (AP) including at leastone of authentication information, charging policy, access priority,registration information, loading, capacity, achievable throughput, andservice latency of the WLAN AP.
 21. The UE of claim 14, wherein the WLANinformation is received by the serving base station from a second UE,and wherein the WLAN information comprises scanning result obtained bythe second UE over WLAN frequency channels.